Well, that was weird. I went back, made a new post, typed it all in plain text, and it tagged the url automatically in preview like normal. So, I went back in and added the manual quote tags. It posted a-ok. Strange. lol
Next time, instead of using the URL link, I'll try to remember to just let it tag URLs on first preview. Then I'll edit the post to clean it up. I'm guessing that it's getting messed up between trying to has the post with preview and AutoSave. That's just a guess. No fix needed, it'll present the reasons eventually, I reckon.